The objective of this project is to study the biosynthesis of the surface structures of bacteria - the cell wall and membrane - in relationship to cellular growth and cell division. Streptococcus faecalis ATCC 9790 (faecium) will be the primary subject of this study. Where appropriate, studies will be made of other bacterial species, especially those which differ from Streptococci in shape or mode of division, so that generalizations may be made. Cells (and protoplasts) will be grown in a completely synthetic medium under conditions of "balanced" exponential growth and selected "unbalanced" growth conditions. We are particularly interested in the events which occur during the change from one state to the other - for example, upon recovery of growth after inhibition of protein synthesis (by starvation for selected amino acids or addition of specific antibiotics). We will investigate the dynamics of incorporation, fate and cellular localization of specific radioactive precursors (e.g., L-lysine and D- alanine for cell walls, chloroform-methanol soluble phosphorus and glycerol for cell membranes), by means of the pulse-chase labeling technic. We will study the biosynthetic precursors and enzymes involved. Thermosensitive mutants, defective in some aspect of wall and/or membrane biosynthesis, will be isolated and studied. The physiology and biochemistry of the process of regeneration of a cell wall by forms which are defective in or completely lack the wall structure (osmotically fragile forms, protoplasts, L-forms) will be examined. Electron microscopy will be used in order to correlate physiological and biochemical changes with changes in ultrastructure.